Intravenous (IV) fluid delivery pumps are used to deliver fluid to a patient or to draw out fluid from a patient's body. The delivery of fluid is achieved by using gravity and/or a pump. A typical pump-based IV fluid delivery system includes a pump connected to a fluid reservoir via an inlet tube and to a patent via an outlet tube. During normal fluid delivery operation, the pump moves fluid from the reservoir to the patient at a certain flow rate. The flow rate may be controlled by a medical professional. Certain applications require that the fluid delivery system strictly adhere to the flow rate set by a medical professional.
The actual flow rate of delivery for certain IV fluid pumps presently available in the market is sensitive to variations in upstream and downstream fluid pressures. Such variations occur when the relative elevation of the pump with respect to a reservoir or a patient is changed. Furthermore, small bore IV tubing and filters on the output can result in high output pressures. Certain fluid delivery pumps, e.g., as disclosed in the U. S. Patent Application No. 2009/0035152, use the resiliency property of a membrane in fluid contact with the fluid being delivered to control the rate of flow. In such fluid delivery pumps, negative upstream (inlet tube) or downstream (outlet tube) pressures can cause partial or complete collapse of the flexible membrane of a disposable fluid chamber used with the pumping mechanism. To mitigate the problem, the affected membrane sections of the disposable fluid chamber have traditionally been made from springy, resilient material, such as silicone so that the section can self-inflate against a negative (opposing) pressure. Other methods may include attaching a piston or a pump to the disposable fluid chamber using magnets or other physical devices so that the pump can pull on the chamber as well as push to perform the pumping action. Such methods can often adversely affect the flow rate accuracy, since transitions from pushing to pulling can be difficult to accomplish in a uniform and continuous fashion.